Clarify generic type parameter ordering

[BHUVANSH855]

Summary

Clarify how type parameter ordering is determined for generic classes.

This expands the existing wording in the generics spec to explicitly
cover:

• Generic[...] base classes
• parameterized Protocol[...] base classes
• Python 3.12 generic class syntax

The updated wording also clarifies that a bare Protocol base class
does not affect type parameter ordering.

Closes #2059

[JelleZijlstra]

@BHUVANSH855 please do not keep merging main into your branch unless there is an actual merge conflict.

[JelleZijlstra]

I think we should add a section header "Type parameter ordering", starting at line 487 or so. Currently this is in a section "Arbitrary generic types as base classes", which isn't really apposite.

[JelleZijlstra]

Also, is this already covered sufficiently in the conformance suite? What are the relevant tests that we have?

[BHUVANSH855]

Also, is this already covered sufficiently in the conformance suite? What are the relevant tests that we have?

Addressed the requested changes:

• added a dedicated “Type parameter ordering” section header
• reordered the section so the Python 3.12 generic class syntax appears first
• updated “both examples” to “all of the examples above”

There is already conformance coverage for Protocol[...] ordering in conformance/tests/protocols_generic.py. In particular, the Proto1(Iterable[T_co], Protocol[S, T_co]) example together with the specialization checks verifies that type parameter ordering follows the Protocol[...] subscript order.

This PR expands the spec wording to make the broader ordering rules explicit, including Generic[...], parameterized Protocol[...], bare Protocol, and PEP 695 syntax.